#streams

13 streams interview questions, asked at Google, Sierra, Amazon and 7 more companies. Last asked Sep 2026.

Find timed-out RPC calls from start and end logsCodingA service writes one log record when a remote procedure call starts and another when it ends, and the log is in time order. Given the log and a timeout, report every call that ran…
Last asked Sep 2026
+1
Merge ordered streamsCodingMerge several ordered input streams into one ordered output without loading any stream fully into memory. Reported on 1point3acres' Sierra bank; reconstructed in our own words.
Last asked Sep 2026
Streaming top-K frequent elements with O(1) updatesCodingElements arrive one at a time from an unbounded stream. Design a structure that can report, at any moment, the K elements seen most often so far. Clarify what K is and whether it…
Last asked Sep 2026
+1
Find the median from a data streamCodingNumbers arrive one at a time; after any of them, return the median of everything seen so far. Keep two heaps (a max-heap for the lower half and a min-heap for the upper half)…
Last asked Sep 2026
Unique and most frequent keys in a recent time windowCodingEvents arrive with a key and a timestamp. Build a structure that, for the most recent window of time, answers which keys appeared exactly once and which key appeared most often…
Last asked Aug 2026
Deduplicate and order logs from batch and streaming sourcesCodingLog records come both in batches and as a live stream; some are duplicates and some arrive out of order. Produce a single output that has each record once, in timestamp order…
Last asked Jul 2026
Stream of points: remove any pair within a distanceCodingPoints arrive one at a time. When a new point is within a given distance of a point already stored, remove that pair; otherwise store the new point. Keep each step fast as the…
Last asked Jun 2026
Count words in a text streamCodingWrite a class that receives text in chunks from a stream and keeps a count of how many times each word has appeared, with a method to read the count of a word (or the most common…
Last asked Apr 2026
Raise alerts from a streaming vmstat feedCodingRead the output of vmstat as it streams, line by line, parse the columns, and print an alert whenever a chosen metric crosses a threshold. Keep it working on a stream that never…
Last asked Apr 2026
Sliding window conversation scores with percentilesCodingTrack conversation quality scores in a sliding window and answer percentile queries over the current window. Reported on 1point3acres' Decagon bank; reconstructed in our own words.
Last asked Apr 2026
Assemble objects from chunks of an async streamCodingReads from an asynchronous stream return arbitrary chunks of bytes, so one object can be split across reads and one read can hold several objects. Write code that buffers the…
Last asked Feb 2026
Ordered integer streamCodingMaintain an integer stream that yields values in order as out-of-order inserts arrive. Reported on 1point3acres' Sierra bank; reconstructed in our own words.
Multiples streamCodingGenerate the infinite stream of multiples (or Hamming-like numbers) lazily, yielding values in order on demand. Reported on 1point3acres' Sierra bank; reconstructed in our own…